Question

What is common between xerarch and hydrarch succession?

• A. Pioneer species
• B. Habitat
• C. It eventually leads to mesic conditions
• D. Both a and b

Answer 1

The correct option is D Both a and b

Ecological succession is a steady and gradual change in the composition and structure of communities of an area with the changing environment. It is predictable, sequential and in accordance with the changing physical environment.
Based on the nature of the habitat, succession of plants are of two types :

• Hydrarch succession - It takes place in wetter areas and progression takes place from hydric (very wet condition) to mesic conditions (medium water conditions). The pioneer species in hydrarch succession are phytoplanktons which contribute to humus formation.
  
• Xerarch succession - It takes place in dry areas, and progresses from xeric (very dry condition) to mesic conditions. Lichens are the pioneer species in xerarch succession, which secrete acids that dissolve rocks, leading to weathering and soil formation.

Hence, both wet and dry water conditions lead to mesic conditions.